Time And Epochs

Overview Dates Time And Calendars#

Some information on Overview Dates Time And Calendars.

Microsoft TIME#

Microsoft TIME is different.


The timestamp, as used in the UUID RFC 4122 is a 60 bit value, representing the number of 100 nanosecond intervals since 15 October 1582 00:00:000000000 This guarantees that there would be no duplicates in UUID until 3400 AD. (Then What? ;-) )

Unix Time#

Unix Time is a NumericDate


OpenVMS, it's 00:00:00 of November 17, 1858 (base date of the United States Naval Observatory's ephemerides)


Macintosh, it's the midnight beginning January 1 1904. (MacOS Epoch)

System time is measured in seconds or Tick past the epoch.

Google Sheets#

Google Sheets uses a form of epoch date that is commonly used in spreadsheets. The whole number portion of the value (left of the decimal) counts the days since December 30th 1899. The fractional portion (right of the decimal) counts the time as a fraction of one day. For example, January 1st 1900 at noon would be 2.5, 2 because it's two days after December 30th, 1899, and .5 because noon is half a day. February 1st 1900 at 3pm would be 33.625.

Note that Google Sheets correctly treats the year 1900 as a common year, not a leap year.

More Information#

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